In Dedicated server,client get value is null at blueprint

When I was in a dedicated server environment, I declared a UserWidget variable in C++ and exposed it to the blueprint.

It works fine in C++, but fails in Blueprints.

But in a stand-alone environment, it is normal.

.h

	//对话UI
	UPROPERTY(BlueprintReadOnly)
		class USignalDialogWidget* SignalDialogWidget;

.cpp

void ABaseCharacter::BeginPlay()
{
	Super::BeginPlay();

	GameState = Cast<APlayingGameState>(GetWorld()->GetGameState());

	if(GetLocalRole() == ENetRole::ROLE_AutonomousProxy)
	{
		SignalDialogWidget = CreateWidget<USignalDialogWidget>(GetGameInstance(),LoadClass<USignalDialogWidget>(nullptr,TEXT("WidgetBlueprint'/Game/UI/Game/Signal_Dialog.Signal_Dialog_C'")));
		SignalDialogWidget->AddToViewport();
		SignalDialogWidget->ShowDialog(TEXT("机体状态检测:通过。  通讯信号:正常。 目标:摧毁敌方母舰。  开始执行任务。"),0.15,3.0);		
	}
}

blueprint:

error:

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